Amplification of Plunging Flows in Bedrock Canyons

Abstract

Incision in bedrock channels controls the rate of landscape evolution by setting the pace of topographic response to tectonic uplift and climate-controlled precipitation patterns, while also establishing the lower boundary condition for their watersheds (Whipple et al., 2013). Bedrock rivers are hard points in the landscape that must be cut through to lower the elevation of the whole landscape (Rennie et al., 2018;Venditti, Li, et al., 2020). Therefore, incision in bedrock channels sets the size, shape, and relief of mountain ranges (Whipple, 2009;Willett, 1999). Sediment particle movements that cause bedrock incision are well known and there are models for many of the processes (c. f.

Plunging Flow and Coherent Turbulent Structures in a Straight Pool‐Riffle

“…J. MacVicar & Rennie, 2012). This distribution of flow matches with expectations from mechanical studies of CDF (Monty et al, 2011;Simpson et al, 1981;Wu et al, 2006), but does not support field observations of fast flow near the channel bed, described by other researchers as a "high velocity core" that can plunge toward the channel bed (Booker et al, 2001;Hurson et al, 2022;W. L. Jackson & Beschta, 1982;Kang & Sotiropoulos, 2011;Keller, 1971;D.…”

“…Another significant gap remains in the pool‐riffle literature because of the observed “skimming” flow in some laboratory experiments, where the fastest flow occurs near the water surface in the pool rather than near the channel bed (B. J. MacVicar & Best, 2013; B. J. MacVicar & Rennie, 2012). This distribution of flow matches with expectations from mechanical studies of CDF (Monty et al., 2011; Simpson et al., 1981; Wu et al., 2006), but does not support field observations of fast flow near the channel bed, described by other researchers as a “high velocity core” that can plunge toward the channel bed (Booker et al., 2001; Hurson et al., 2022; W. L. Jackson & Beschta, 1982; Kang & Sotiropoulos, 2011; Keller, 1971; D. M. Thompson et al., 1999; Venditti et al., 2014; Whiting & Dietrich, 1991). Keller (1971), for example, originally made his measurements near the bed of the pool based on the hypothesis that they would increase faster with flood stage than those higher in the flow.…”

“…First is the recent work of Hurson et al. (2022) on plunging flow in canyons. Though they noted that $${F}_{r}< 1$$ at all times, the physical description of the formation of a backwater upstream of the canyon indicates that the flow regime may be important for understanding the occurrence of plunging flow in some cases.…”

“…Such an effect is useful because it supports the D. M. Thompson et al (1999) model for the evacuation of material from a pool, but it does not explain plunging flow in the pool head. Plunging flow in canyon pools has been noted (Hurson et al, 2022;Venditti et al, 2014) and does not appear linked to the above cited effects.…”

Experiment on the Hydrodynamic Characteristics of Plunging Flows in Bedrock Canyon Bends

“…The local higher and lower shear stresses caused by steep near-bed velocity gradients along plunging velocity cores drive the morphology and patterns of incisions in canyons (Venditti et al, 2014). The dynamics, persistence, and occurrence of plunging flows affect the vertical bedrock incision rate (Hurson et al, 2022). turbulent kinetic energy (Blanckaert, 2015;Ferreira Da Silva & Ebrahimi, 2017).…”